1. Technical Field
This invention relates to bonding apparatuses and techniques and, more particularly, to an apparatus and method for bonding automotive fiber reinforced plastic (FRP) members together.
2. Discussion of the Related Art
Various techniques are currently employed for bonding fiber reinforced plastic (FRP) members together for use in automotive body applications such as, but not limited to, hoods, doors, bumpers, and the like. There has been an outgrowth in the number of apparatuses and methods available for producing bonded FRP assemblies due to the growing trend in the automotive industry to replace heavier metal components with plastic assemblies. These assemblies are typically bonded by heating an adhesive placed between the mating surfaces of two FRP members to a temperature exceeding its curing temperature.
FIGS. 1-3 illustrate in simplified manners, examples of well known bonding techniques that use heat to bond an FRP assembly consisting of FRP members 10 and 12 with adhesive 14 placed therebetween. FIG. 1 illustrates dielectric heating apparatus 16 that produces radio frequency electrostatic fields between electrode 18 and block member 20. The electrostatic fields quickly heat adhesive 14 to a temperature above its curing temperature to thereby bond FRP members 10 and 12. Commonly assigned U.S. Pat. No. 4,941,936 to Wilkinson et al. and U.S. Pat. No. 4,941,937 to Iseler et al. disclose examples of dielectric heating techniques which are hereby incorporated herein by reference. Dielectric heating techniques have the advantage of reducing cycle times along with the accompanying disadvantage of heating an FRP assembly in a manner that is difficult to control and maintain.
FIG. 2 illustrates bonding apparatus 22 that utilizes cartridge heaters 28 for heating metal block members 24 and 26. Block members 24 and 26 in turn heat the air flowing through air circuits 30, a portion of which, flows through openings 32 for heating adhesive 14 between FRP members 10 and 12. One disadvantage with this type of bonding technique is that it requires a large supply of compressed air to operate efficiently.
FIG. 3 illustrates bonding apparatus 34 that utilizes heated steam and/or hot water flowing through passages 40 for heating metal block members 36 and 38. Block members 36 and 38 in turn heat adhesive 14 between FRP members 10 and 12. This bonding technique has the disadvantage of requiring a high cycle time when compared to the bonding techniques illustrated in FIGS. 1 and 2.
When bonded FRP assemblies are used in exterior automotive body applications, it is of the utmost importance that the bonding technique employed does not adversely effect the surface qualities of the exterior FRP members and that the technique provides even bonding not withstanding the size of the FRP members.
Thus, it would be desirable to produce a bonding apparatus that improves the surface qualities of a resulting FRP assembly and that provides uniform bonding strength throughout the assembly. Further, it would be desirable to provide a bonding technique that expeditiously adheres a first FRP member to a reinforcement FRP member without affecting surface qualities or bonding strength characteristics.